May 24, 2017

Subsurface wastewater option rejected

Erin Town Councillors still want to explore alternative technologies for Erin’s future wastewater system, but discharging treated effluent into the ground instead of the river will not be one of them.
They received a detailed technical report last week by engineer Gary Scott of Ainley Associates that says a subsurface disposal system would be impractical, risky and more costly than surface disposal. The analysis is backed up by Credit Valley Conservation and the Ministry of the Environment and Climate Change.
“It’s not competitive with surface water disposal and doesn’t give any cost advantage,” said Scott. Council authorized the investigation last year.
“The Master Plan had mentioned it, but subsurface disposal hadn’t been looked at in detail, so we have plugged that hole.”
This will avoid the possibility that the overall study could be challenged and delayed for failing to have studied sufficient options.
The projections are based on the possibility of “full build-out”, meaning that homes could be built over a 20-30 year period on all of the lands within the urban areas of Hillsburgh and Erin village that are already designated for that use in the Official Plan.
Current homes in Erin village would generate wastewater of 2,244 cubic metres per day (m3/d), but that could more than double to 4,767 m3/d. The Hillsburgh flow could quadruple, from 600 to 2,400 m3/d.
For a subsurface discharge bed, Erin village would need 40 hectares (98 acres), set back at least 300 metres from any creek or wetland. Such lands do not exist near Erin village, even if they could be purchased.
“The MOECC would likely require a spare bed,” said Scott. “There is a history of failure for subsurface systems in North America and Europe. The ministry is cautious in approving them.”
Hillsburgh would require a 19.5 hectare (48 acre) lot, which Scott say may be possible. But he said the costs of building and maintaining subsurface disposal in Hillsburgh, plus traditional river disposal in Erin village, are 10-20 per cent higher than pumping Hillsburgh sewage to a single treatment plant in Erin village.
Preliminary estimates (at full build-out) show the cost of treating waste at two separate areas at $71 million, compared to $61.7 million at a single Erin village site. That does not include the huge separate cost of building the collection pipe system throughout the villages.
Previously, new growth was expected to be limited to 6,000 residents. But a strategy suggested last year (but not yet approved by council) could see well over 10,000 new residents. Some existing neighbourhoods could be exempt from having sewers, and intensive treatment of sewage could allow for more effluent being allowed in the river.
Full details of the strategy are to be presented at a Public Information Centre (PIC). This has been delayed, and is expected this spring. The current phase of the Environmental Assessment is intended to research various practical options for collection and treatment of wastewater.